Storage racks or shelving units are common in homes, offices, garages, pantries, and many other areas. To increase the functionality of such storage racks, it is often desirable to have flexibility in positioning shelves or even entire shelving units relative to each other, etc. while still providing a structurally sound unit or assembly of units. When shelving units are assembled in a side-by-side or end-to-end relationship, vertical support portions of the shelving units are often duplicated and placed to abut one another. To increase stability, the duplicate support portions may be coupled to one another.